STUDY OF PROPERTIES OF MODIFIED LIQUID GLASS

ABSTRACT

This article examines the use and properties of modifications based on liquid glass in the construction industry. Bottles containing liquids of different contents were used as the basis for the study. The process of modifying liquid glass was carried out in a magnetic stirrer. At the beginning of the process, the composition of liquid glass was analyzed and it was determined that its composition was metasilicate and bisilicate . To modify liquid glass, urea-formaldehyde resin (UFR) was used. During the synthesis process, the pH value of the medium was also taken into account . Because sodium silicates are strong bases and weak acids. In this case, liquid glass as a result of hydrolysis can always form H⁺ and OH^- ions . Silicid acids are weak and therefore dissociate little . In liquid glass, OH ions are always in excess, so it has a characteristic alkaline environment (pH = 12-14). As a result, it becomes somewhat easier to modify it with acidic substances.

АННОТАЦИЯ

В данной статье изучено применение и свойства модификаций на основе жидкого стекла в сфере строительства. В качестве основы исследования были использованы бутылки с жидкостью разного содержания. Процесс модификации жидкого стекла проводился в магнитном мешалке. В начале процесса был проанализирован состав жидкого стекла и установлено, что его состав метасиликатный и бисиликатный. Для модификации жидкого стекла использовалься карбамид формальдегидная смола (КФС). В процессе синтеза также учитывали значение pH среды. Потому что силикаты натрия являются сильными основаниями и слабыми кислотами. При этом жидкое стекло в результате гидролиза всегда может образовывать ионы H⁺ и OH^-. Кремниевые кислоты слабы и поэтому мало диссоциируют. В жидком стекле ОН-ионы всегда в избытке, поэтому оно имеет характерную щелочную среду (рН = 12-14). В результате модифицировать его кислотными веществами становится несколько проще.

Keywords: liquid glass, metasilicate, bisilicate , magnetic stirrer, mixture, polyvinyl acetate, coagulation

Ключевые слова: жидкое стекло, метасиликат, бисиликат, магнитная мешалка, смесь, поливинилацетат, коагуляция

Introduction. The main objective of introducing heavy-duty mixtures is to increase evaporation and regeneration. Knockout problem liquid glass mixtures through six pores remains an unresolved brand. In connection with the above, it is advisable to strive for the performance of “ideal” binders, to which the following requirements can be imposed: hardening at room temperature; minimal energy consumption for molding ; compatibility of the mixture for the manufacture of cores and molds; the possibility of mechanizing the production of cores and molds; eliminate the need for special processing of metal tools; insensitivity to the quality and temperature of sand; reuse of the mixture; lightness, knockout and regenerability ; high strength and stability of the properties of the rod and shape at pouring temperature; the possibility of obtaining a high-quality casting surface without the use of non-stick coatings; cost-effectiveness and accessibility; ensuring the possibility of automation of mixing preparation[1-5].

None of the connecting systems fully meets these requirements. Further improvements in binder production, technology and equipment will increase the use of new processes and possibly reduce wet mold[6-8].

It is difficult to predict which binding system will dominate in the future. The advantages of liquid glass mixtures are their non-toxicity , non-flammability, availability and low cost. They are non-flammable and have no side effects when used in industry[9].

The hardening of mixtures with liquid glass occurs due to gelation, as a result of which strong adhesive bonds are formed in the binder itself and adhesive bonds in the sand grain itself. This effect can be achieved in the following cases: reducing the amount of water in a bottle with liquid; Decrease in pH value or increase in liquid glass modulus (M). But high-modulus liquid glasses provide lower strength to mixtures than low-modulus ones, and therefore are rarely used [10-13].

Liquid glass, depending on the module, freezes at temperatures from -2 to -11ºС, boiling point – from 100.5 to 102.0ºС.

The liquid glass solution contains: metasilicate Na₂ O•SiO₂ or bisilicate Na ₂ O• 2SiO_{2 ,} there are 2Na⁺ ions  and (SiO₃)²ˉ or (Si₂O₅)²ˉ . Liquid glass with a low modulus can be imagined as an ideal solution containing monosilicate (SiO₄) ⁴ˉ and bisilicate ions (Si₂O₅) ²ˉ, and in high modulus - increased content of SiO ₂ in colloidal form.

Materials and methods. Due to hydrolysis, liquid glass always contains H⁺ ions and OH ^- . Silicic acids are weak and therefore slightly dissociated . In liquid glass, OH^- ions are always in excess, which is why it has a characteristic alkaline reaction (pH = 12–14).

Solutions of sodium silicates are stable only at high pH values ; its reduction leads to rapid gelation. This mechanism is used in the development of self-hardening compounds. For example, at high pH, the addition of ether results in hydrolysis.

The main properties of liquid glass are modulus and density. The modulus of liquid glass is the ratio of the mass fraction of silicon to the mass fraction of sodium oxide.

Table 1

Dependence of density on solution concentration

The density of liquid glass is determined mainly by the water content (inverse relationship). Its modulus has a certain influence on the density of liquid glass: as the modulus increases, the density of liquid glass decreases. This dependence is also known for silicate blocks.

Results and discussion . The viscosity of liquid glass depends on temperature and concentration; the effect of temperature was studied in a magnetic stirrer. In this case, changes in viscosity were observed under the influence of the silicate modulus and temperature. (Table 2).

Table 2

Silicate modulus and temperature

As can be seen from the results of Table 2, viscosity increases with increasing modulus due to the enlargement of silicate frameworks under the influence of microwaves. It can be assumed that the viscosity increases due to an increase in the matrix under the influence of time. The change in viscosity may be small due to the small influence of the silicate modulus on intermolecular interactions and molecular polymerization in small solutions.

Many organic substances, such as acetone, aldehydes, phenol, cause coagulation of liquid glass. At the same time, other organic additives (cane sugar, glucose, glycerin, dextrin, bitumen) do not cause coagulation of liquid glass.

In addition to the positive properties of liquid glass listed above, its disadvantage is its solubility in water. The problem of increasing the adhesion of liquid glass and improving its properties by reducing solubility in water is relevant. Based on the above, the factors influencing its rheological properties were studied.

The composition of liquid glass with a 10% solution of water-soluble highly adhesive polymers, urea-formaldehyde resins and a 10% solution of acrylic emulsion has been studied. It was observed that the polymer forms a binary mixture with liquid glass. An emulsifier was used for homogenization. The viscosity of the homogeneous composition and its state after mixing in a magnetic stirrer were studied. The results obtained are presented in Table 3.

Table 3

Results

The reason for the increased viscosity of acrylic emulsion compared to urea-formaldehyde resin is due to the low ability of the ester in the side chain of urea-formaldehyde resin to enter into binding or intermolecular interaction. Various functional groups in the acrylic emulsion chain result in increased adhesion by placing the silica within the tetrahedral framework matrix so that it can bond with the polysilicate in the water glass. Due to the stirring vibrations of the molecule, its energy increases and intermolecular bonds are created. Intermolecular communication is achieved by reducing the potential barrier in the molecule. Based on studies of the effect of mixing on the adhesion of liquid glass, its increased viscosity and improved adhesion are explained by the fact that its molecules have entered a macrostate.

The obtained samples were used to obtain high-quality cement in aqueous and saline environments in the construction industry. The dehydrated layer of ceramic and cement-lime sand samples has different characteristics; the comparative pore surface is more developed and differs in the rate and method of its formation. An important role in the formation of the system is played by the fact that the molecules of the synthesized organic-inorganic system have high adsorption activity. The reason for this is the nature of hydrate formation of the surface, which can be explained by its specific surface with more developed adsorption activity in relation to cement-sand samples and polymer molecules. Therefore, the hydrated -OH group in clinker minerals of cement stones of the -OH group is located in the active center on the surface and intermolecular interaction occurs with them.

The scientific results obtained show that coatings based on local raw materials provide effective protection of building structures and materials from salts and water; they were used in the construction of standard houses and industrial buildings. When using working solutions of 3% poly(oligo)mers based on liquid glass, the water absorption of cementitious materials is reduced by 50%. Due to the fact that the polymer used has a plasticizing property, it was noted that it caused an increase in the grade of cement due to the fact that it slowed down the cement setting process by 41%. Methods for increasing the moisture resistance of building structures and materials, highly dispersed inert fillers using hydrophobic substances, and creating modified mixtures are substantiated.

Conclusion. A change in the viscosity of the composition was observed due to the adhesion and macromolecularity of the composition. When stored in a magnetic stirrer, it was noticed that the polymer and the polysilicate molecule formed a single mass under the influence of mixing, which could cause a change in its viscosity.

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